Image receiving material for the silver salt diffusion process

ABSTRACT

A LIGHT-INSENSITIVE IMAGE RECEIVING MATERIAL FOR THE SILVER SALT DIFFUSION PROCESS COMPRISING AN IMAGE RECEIVING LAYER WHICH CONTAINS A COMPOUND OF THE MERCAPTO TRIAZOLE SERIES.

United States Patent 3,674,481 IIVIAGE RECEIVING MATERIAL FOR THE SILVER SALT DIFFUSION PROCESS Anita von Konig and Werner Liebe, Leverkusen, and

Helmut Timmler, Wuppertal-Vohwinkel, Germany, assignors to Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany No Drawing. Filed May 27, 1970, Ser. No. 41,085 Claims priority, application Germany, June 14, 1970, P 19 30 339.0 Int. Cl. G03c 5/54 U.S. C]. 96-29 2 Claims ABSTRACT OF THE DISCLOSURE A light-insensitive image receiving material for the silver salt diffusion process comprising an image receiving layer which contains a compound of the mercapto triazole series.

The invention relates to an image receiving material for the silver salt diffusion process which contains heterocyclic dimercapto compounds for improving the stability of the finished silver images.

The silver salt diffusion process for the direct production of positives is described in French Pat. No. 879,995. In this process, the unexposed and undeveloped silver halide of an exposed silver halide emulsion layer is dissolved during development, and transferred to an image receiving layer, which is in close contact with the exposed silver halide emulsion layer, so as to produce a positive image in the image receiving layer upon development of the transferred silver halide in the presence of development nuclei which are uniformly distributed in the image receiving layer. The terms negative and positive are to be understood as being only in relation to one another, i.e. direct negatives can also be obtained from a negative original by the same process.

The complex forming agent required for dissolving the unexposed and undeveloped silver halide, particularly sodium thiosulfate, is added either to the developer or to the image receiving layer. The finished copy, therefore, still contains thiosulfate in quantities of about 0.5 to 1.5 g./m. The presence of compounds which form complexes with the silver salt gives rise to the disadvantages that these complex forming agents reduce the concentration of silver ions and thereby facilitate the oxidation of the metallic silver. The image silver is, therefore, easily attacked by oxidation and converted into a complex or simple silver salt. This causes particularly in a moist atmosphere fading of the silver image or a brown discoloration of the silver in the image. The image silver disappears particularly readily in those areas where only a little silver was deposited on the copies because of short contact times. In practice, contact times of about 5 to seconds have recently become customary so that only a little silver is deposited, the stability of which is, therefore, reduced in the presence of sodium thiosulfate.

It is among the objects of the invention to modify the silver salt diffusion process so that the silver images obtained will have improved stability.

We now have found an image receiving material for the silver salt diffusion process which comprises an image receiving layer which may contain development nuclei, the image receiving layer containing a mercapto triazole derivative of the following formula:

3,674,481 Patented July 4, 1972 ice N i HSO Clt l li in which R =a mercapto group or the group R (I) an amino group or a substituted amino group, (II) together with R the ring members required for completing a 2-mercaptothiodiazole ring or (III) in the case of a bis-triazole compound, R =R R =hydr0gen; alkyl containing up to 8 C-atoms, preferably containing 1 to 3 C-atoms; aryl preferably a radical of the phenyl or naphthyl series; aralkyl such as benzyl or phenylethyl; cycloalkyl such as cyclohexyl; or an amino group; the radicals, in particular phenyl rings, may be substituted, e.g. with halogen atoms such as chlorine or bromine; or alkyl or alkoxy groups containing preferably up to 5 C-atoms, or hydroxyl groups;

Y=an alkylene chain containing 3 to 10 methylene groups which are interrupted by hetero atoms such as oxygen or sulfur or imino groups.

Suitable compounds are summarized below:

e Decomposed.

The preparation of these compounds has been described in US. Pat. No. 3,647,451.

M.P. C.

processed.

hydrazide with canbon disulfide in pyridine as described in Acta Chemica. Scandinavica 15, pages 1295-1302 (1961). The compounds according to the invention may, of course, also be present in the corresponding thione form.

The concentration of the mercaptotriazole compounds in the image receiving layer may vary within wide limits. This depends on the requirements of the reproduction process and eifectivenes of the particular compounds. Quantities of between 1 and 300 mg./m. and preferably between 5 and 100 mg./m. of image receiving layer, have generally been found to be sufficient. The triazole derivatives are soluble in aqueous alkalies or dimethylformamide and may be added in form of solution to the casting solutions for the production of the image receiving layer.

The image receiving material generally consists of an image receiving layer on a suitable support. The support may be the known sheet-like materials, particularly paper, preferably baryta-coated paper.

Suitable binders for the image receiving layer are the hydrophilic film-forming materials usually used for this purpose, e.g. proteins, particularly gelatin, also starch or starch derivatives, alginic acid or derivatives thereof such as salts, esters or amides, also carragenates or synthetic binders such as polyvinyl alcohol, polyvinyl pyrrolidone, partially saponified polyvinyl acetate, etc.

According to a preferred embodiment, the image receiving layer contains development nuclei of the usual type, e.g. sulfides or selenides of heavy metals such as cobalt, nickel, zinc or silver, and, furthermore nuclei of these metals. Modified nuclei of heavy metal sulfides or heavy metal selenides consisting of a core of an inert material, of a metal or of a sulfide or selenide other than that present in the surface, are also suitable. Nuclei of this type have been described in German Pat. No. 1,201,997 or in US. Pats. Nos. 2,698,236; 2,698,238 or 2,698,245.

The image receiving layers may, of course, contain the usual additives, particularly blue toners. Image receiving layers of this type have been described in German Pats. Nos. 1,108,563; 1,124,355; 1,124,354 and 1,153,247. The usual light-sensitive materials which generally contain a light-sensitive silver halide gelatin emulsion layer are suitable for the modification of the silver salt diffusion Quantities or 1 to 300 mg., preferably 50 to 250 mg./l.

EXAMPLE 1 .Image receiving material A baryta-coating of the following solution is applied to a support of paper (80 g. per m?);

6 g. of a 50% aqueous suspension of barium sulfate, ml. of a 10% aqueous gelatin solution, 8 ml. of a 50% aqueous emulsion of polyvinyl acetate,

(Water up to 100 ml.)

The baryta layer is dried and then coated with an image receiving layer of the following casting solution:

4.5 g. of propylene glycol alginate 12.5 mg. of silver sulfide in the form of an aqueous colloidal solution,

20 ml. of a 50% aqueous gelatin solution 1.5 ml. of a 30% aqueous solution of potassium bromide, 1.2 m1. of a 30% aqueous solution of saponin,

7.5 g. of sodium thiosulfate,

(Made up with water to 300 ml.)

The layer is applied in such a thickness that it contains about 1.1 g. of sodium thiosulfate per m9.

Another layer of the following casting solution is applied on the first layer:

3.5 g. of sodium alginate,

10 g. of sodium thiosulfate,

0.8 ml. of a 30% aqueous solution of potassium bromide,

8 ml. of a 30% aqueous solution of saponin,

0.5 ml. of a 1% alcoholic solution of 3-mercapto4,5-dimethyl-1,2,4-triazole (Made up with water to 350 ml.)

This layer is applied in such a thickness that it contains about 0.6 g. of sodium thiosulfate per 111. .Y

9 samples of the above composition are prepared and a certain quantity, shown in the following table, of one of the compounds according to the invention is added to each of these samples before casting.

Processing The above image receiving layer is brought into contact with an exposed silver chloride gelatin emulsion layer and developed in the following developer bath, using a conventional processing apparatus:

75 g. of anhydrous sodium sulfite,

15 g. of hydroquinone,

1.2 g. of 1-phenyl-3-pyrazolidone,

12 g. of sodium hydroxide,

1 g. of potassium bromide made up with water to 1 l.

The contact time is 15 seconds. After leaving the apparatus, the negative is separated from the image receiving layer. To test the stability of the silver image, a portion cut out of the finished copy is stored for 24 hours in a vessel over water. Several of these uniformly moist portions of copies are introduced into a polyethylene bag which is inserted into a second bag containing 30 ml. of Water and the bags are sealed. The sealed bags are stored in a heating cupboard at 60 C. for 24 hours and 48 hours, respectively, and the alteration in the silver image is judged at the end of this time. Whereas the silver image of the copies which contain one of the compounds of the invention in the image receiving layer remains black or dark brownish black depending on the length of storage time in moist heat, the comparison sample shows a discoloration varying from brown to pale brown. The maximum density of the various materials is determined on fresh, air dried copies and copies which have been stored in moist heat, using a densitometer customarily employed in the art. The following results are obtained:

Whereas the copies of the control sample are discolored brown to pale brown as a result of storage, the copies which contain the compounds according to the invention remain dark brown to blue-black. Moreover, the figures obtained with the air dried samples show that some of the compounds according to the invention slightly accelerate the deposition of silver.

EXAMPLEZ The light-sensitive silver halide layer contains about 600 mg. of hydroquinone an 150 g. of l-phenylpyrazolidone-(3) per m.

The light-sensitive layer is exposed, contacted with an image receiving layer as described in Example 1 and developed in the following activator solution instead of in the developer bath indicated in Example 1:

G. Sodium sulfite sicc. 40 Sodium phosphate sicc. 30 Sodium hydroxide 1.5 Sodium thiosulfate cryst. 1 Potassium bromide 1 Water to up to 1 1.

After a contact time of seconds they are separated. Subsequent processing and testing are carried out as described in Example 1. The quantities of the mercapto triazoles added to the image receiving layer are shown in the following Table:

Whereas the blacks of the control sample are discolored to pale brown in the course of storage, the copies containing the compound according to the invention remain dark brown to blue black.

EXAMLPE 3 190 mg. of compound 17 or 160 mg. of compound are added per liter to an activator bath as described in Example 2. The material is then processed in a similar manner to the control sample in Example 1 or 2. Here again, a marked improvement in the loss in density on storage in moist heat is observed. When approximately 100 DIN A 4 copies are produced in 1 l. of activator, a sludge which gives it a very dark discoloration is formed in the activator which does not contain additive and the apparatus becomes severely soiled, whereas in the activators which contain additives a pale sludge is formed which is hardly visible and forms only a slight deposit on the walls of the apparatus.

We claim:

1. A light-insensitive image receiving material for the silver salt difiusion process comprising an image receiving layer which contains a compound of the following formula:

I 1 HS-C/ o-iu I l wherein R =a mercapto group or the group R3 YC o-sn R (I) an amino group (H) together with R the ring members required for completing a Z-mercapto-thiadiazole ring or (III) in the case of a bis-triazole compound, R =R R =hydrogen, alkyl containing up to 8 C-atoms, aryl,

aralkyl, cycloalkyl or an amino group;

Y=an alkylene chain containing 3 to 10 methylene groups which are interrupted by oxygen, sulfur or imino groups. 2. A silver salt diffusion process in which an exposed recording material which contains at least one silver halide emulsion layer is developed in contact with an image receiving material in the presence of a heterocyclic mercapto compound of the following formula:

l t E ns-o c-iu wherein R =a mercapto group or the group s 1'q -Y-fi \(IJSH N l References Cited UNITED STATES PATENTS 4/1969 Wilrijk 9629 7/1950 Knott 7 NORMAN G. TORCHIN, Primary Examiner I. L. GOODROW, Assistant Examiner US. Cl. X.R.

Patent NO. 8 Dated Agril 13, 1971 Inventor(s) James A. Pyne, Jr. e't. a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet, insert [73] Assignee The Garrett Corporation, Los Angeles, Calif., a corp. of California This certificate supersedes Certificate of Correction issued May 2, 1972;

Signed and sealed this 12th day of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents :ORM PC4050 (10459) uscoMM-Dc 60376-P69 ",5. GOVERNMENT PRINTING QFFICEI I969 O-356-334. 

